For example, in 31-TET, all tones are accessible via (double) sharps or (double) flats on CDEFGAB. So there exists key signatures, for example, D double-flat major. (That's same as C half-sharp major.) Wikipedia has a comprehensive list of the keys.
But what for 24-TET? The in-between tones are not accessible via sharps nor flats on CDEFGAB. I can't think of the key signature, for example, C half-sharp major. How should they be denoted?